Film alignment mechanism and frame counter resetting mechanism

ABSTRACT

A camera for use with film bearing a series of latent pre exposed images for subsequent user-exposure, comprises a film sprocket wheel ( 34 ) extending into a film passageway, the sprocket wheel comprising a wheel having a plurality of equidistantly-spaced teeth one ( 42 ) of which is visually distinguishable from other teeth, for example being formed of a contrasting colour.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a mechanism suitable forensuring alignment within a camera of film having pre-exposed latentimages thereon, and to a camera incorporating such a mechanism, and to afilm frame counter resetting mechanism.

[0002] It is known to provide photographic film which has been partlyexposed in regions of each film frame with an image which is retained asa latent image. The user who loads the film then exposes the film in thenormal manner in a specially adapted camera. The camera includes somemasking arrangement to mask out the area of the film which bears thelatent images, so that these are not double-exposed. When the film hasbeen exposed by the user, it is processed and developed in the normalway, the finished pictures bearing both the pre-exposed images providedby the manufacturer (hereinafter referred to as “pre-exposed images”),and the user-exposed images thereon. For example, it can be arrangedthat the film is pre-exposed with a decorative strip which carries amessage such as “happy birthday” or “wish you were here”, the cameraincluding a strip-like mask in the exposure window to preventdouble-exposure of the pre-exposed film region.

[0003] It has been previously proposed by the applicant to provide sucha film in a package or assembly comprising a standard 35 mm cassette anda second spoolless film container into which the film is wound extendingfrom there to the cassette. Such a film package is disclosed for examplein applicant's U.S. patent application Ser. No. ______. In use, theassembly is fitted into the camera with the cassette and film containerarranged on opposite sides of a film exposure window. As pictures aresuccessively taken the film is progressively wound out of the filmcontainer back in the cassette, finally being wound back fully into thecassette which can then be removed by the user for developing andprocessing. The film container is then discarded.

[0004] A particular problem arises in seeking to align the film in thecamera, since it is necessary that the film be precisely positioned inthe camera so that the pre-exposed images align precisely with theexposure window of the camera and hence the user-exposed images.

[0005] In one aspect the present invention is directed to ensuring thisalignment.

SUMMARY OF THE INVENTION

[0006] In a first aspect the invention provides a camera for use withfilm bearing a series of latent pre-exposed images for subsequentuser-exposure, comprising a film sprocket wheel extending into a filmpassageway, the sprocket wheel comprising a wheel having a plurality ofequidistantly-spaced teeth one of which is visually distinguishable fromthe other teeth.

[0007] The alignment tooth may be formed of a different colour to theother teeth, either by painting the alignment tooth or moulding it of adifferent coloured plastics material.

[0008] In one embodiment the sprocket wheel comprises a main wheel parton which said other teeth are formed, and said alignment tooth is formedof a separate part securable to said main wheel part. These may beformed of moulded plastics parts where the plastics are of contrastingcolours. The main wheel part may define a part-annular recess, and thealignment tooth extends from a part-annular insert receivable in saidrecess. The sprocket wheel may be operatively connected to a shuttermechanism and wind-on mechanism where rotation of the sprocket wheel isarranged to effect re-cocking of the shutter mechanism. The wind-onmechanism prevents rotation of the sprocket wheel when the shutter isre-cocked. In the re-cocked state of the shutter mechanism the alignmenttooth extends rearwardly within the camera towards the film passageway.

[0009] In a further aspect the invention resides in a sprocket wheel asdefined above.

[0010] In a further aspect the invention resides in a method of loadingfilm bearing a series of pre exposed latent images for subsequentuser-exposure into a camera having a film sprocket wheel operativelyconnected to a shutter mechanism and provided with a film alignmenttooth, comprising the steps of: a) opening the camera back; b) rotatingthe film sprocket wheel until the film alignment tooth thereof extendstowards the film passageway, and until the shutter mechanism isre-cocked; c) inserting film into the camera so that an alignment markon the film is aligned with the alignment tooth; and d) closing thecamera back.

[0011] A further problem with simple cameras of this type where the userreloads the film is in re-setting of the film frame counter, and asecond aspect of the invention is directed to a mechanism for carryingout this resetting.

[0012] In a further aspect directed to resetting of the film framecounter, the invention resides in a camera having a pair offilm-receiving chambers arranged on opposite sides of an exposure windowbetween which, in use, film extends through a film passageway: a filmsprocket wheel having a plurality of teeth which, in use, engage a filmextending within the film passageway; a film counter drive wheeloperatively connected to the film sprocket wheel driven by rotation ofthe sprocket wheel; a pivotably mounted film frame counter wheel mountedon a displaceable pivot engageable with the drive wheel; and resilientmeans which urge the film frame counter wheel to a reset position inwhich the film frame counter wheel adopts a predefined orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the invention are now described, by way of exampleonly, with reference to the following drawings in which:

[0014]FIG. 1 shows a camera in accordance with an embodiment of theinvention with a back cover opened and a film door removed;

[0015]FIG. 2 shows the insertion of a film package into the camera;

[0016]FIG. 3 shows the film fitted into the camera and correctly alignedwith an alignment sprocket;

[0017]FIG. 4 shows the camera with the back fitted thereon;

[0018]FIG. 5 shows the shutter and wind-on mechanisms of the camera;

[0019]FIG. 6 shows a mechanism for re-setting a film frame counter whenthe counter is at a “start” position;

[0020]FIG. 7 shows the mechanism of FIG. 6 at a position correspondingto part exposure of a film; and

[0021]FIG. 8 shows the mechanism of FIG. 6 on re-setting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] As seen in FIG. 1, the camera, indicated generally by numeral 2,includes a main body part 4 which carries the majority of the operativecomponents of the camera 2, and a front cover part 6 and rear or backcover part 8 which together enclose the main body 4. The main body 4supports a shutter mechanism 9 provided with a lens assembly 11 (FIG.5), a front portion of which extends through an aperture in the frontcover part 6. The main body 4 defines part of a first film-cassettereceiving chamber 12 which receives a film-containing cassette orpatrone 13 of a film package or assembly described further below. Otherstandard film formats can equally be accommodated with appropriatemodification. A second film receiving chamber 14 is arranged at theopposite side of the camera. Between the film chambers 12 and 14 isarranged an exposure window 18 located between upper and lower filmguides 20, 22 which support the film at its edges as it extends betweenthe film chambers. A film passageway for the film to travel between thefilm chambers 12 and 14 is defined between the back cover 8 and opposedregion of the main body 4 and film guides 20, 22. The main body 4, andfront and rear cover parts 6, 9 define an opening at the lower end ofthe film cassette chamber 12, which is closed in use by a removable filmdoor 24, allowing removal of the film cassette 13 through the openingonce the film has been exposed. As is known in the art, the film door 24and adjacent parts of the main body 4 are provided with appropriateadaptations in the form of co-operating grooves on the cover plate 24and flanges on the main body 4 which together ensure light tight closureof the opening.

[0023] The rear cover part 8 is removably fitted to the main body 4.This is achieved by providing at opposite edges a pair of protrusions 25on the main body 4 which snap-fit into apertures 27 on the back cover 8.Alternatively, the back cover 8 can be hingedly secured to the main body4 or the front cover 6 and a releasable latch provided to allow openingand closing of the back cover 8. These arrangements allow the user toreadily open and close the camera for re-loading films therein.

[0024] As is conventional, the camera is provided with a wind-onmechanism including a rotatable film advance wheel or thumb wheel 30having a plurality of teeth held on top of the main body 4 beneath aplate 31, and lower shaped drive shaft 32 which extends into and engagesthe central spool of the conventional film patrone or cassette 13. Themechanism includes a film sprocket wheel 34 located just above the filmexposure window 18, and a film counter. The film sprocket wheel 34 isoperatively connected to the re-cocking mechanism of the shutter, sothat each time the film is wound on one frame by the user (by turningthe film advance wheel), the film sprocket wheel is rotated one turn,which primes the shutter, and in addition prevents further rotation ofthe film advance wheel 30, as is further described below.

[0025] The film is provided in the form of a film assembly comprising afirst film cassette 13 which is a conventional 35 mm cassette orpatrone, and a second film container 15 preferably of a smallerdimension than a conventional cassette, into which the majority of thefilm is pre-wound before the assembly is supplied to the user. Aflexible backing strip 17 is joined to both cassette 13 and container 15to prevent separation of the cassette 13 and container 15 which couldresult in inadvertent withdrawal of film. A cut-out portion 19 isprovided in the backing strip 17 exposing a portion of the film edge. Ascan be seen more clearly in FIG. 3 the film is provided with analignment notch 21 adjacent an alignment perforation 23.

[0026]FIG. 1 shows in the inset a sprocket gear 34 comprising eightsprocket teeth, the gear being precisely dimensioned so thecircumference is the dimension of one film frame so that the teeth fitinto the sprocket holes of a 35 mm film and so that advance of the filmby a single film frame causes precisely a single rotation of the gear.

[0027] The sprocket gear 34 comprises two separate parts, namely a maingear 38 having seven spaced teeth and which defines an annular or apart-annular recess 40, and a slot at the position of the eighth tooth,and a separate alignment tooth part 42 formed on a part-annular portion44 which constitutes an insert fitting into the recess 40. This allowsthe alignment tooth 42 to be moulded out of a different colouredplastics material; for example, the majority of the camera componentsare usually of black moulded plastics; alignment tooth 42 may be of acontrasting colour such as white.

[0028] The shutter mechanism 9 contains a spring-loaded shutter platewhich has an exposed end S arranged to be stroked by a striker 50(further discussed below) of a trigger mechanism 140 for momentarilyflicking the shutter plate (shutter release) and thus opening anexposure aperture behind the lens to permit photographic exposure on thefilm through the exposure chamber 18.

[0029] The trigger mechanism 140 is formed by the striker 50 which ishorizontally pivotable and an assembly of the sprocket 34 and an uppercam 70 which are axially inter-engaged for simultaneous horizontalrotation. The striker 50 has first, second and third side projections51, 52 and 53 and is spring-loaded by spring 90 to, on release, turn inthe anti-clockwise sense (viewed from above) and also to move upwards,thereby urging the second projection 52 to stroke the shutter plate endS and urging the third projection 53 against the cam 70.

[0030] The sprocket 34 is keyed to the cam 70 so that upon movement bythe film-advancing wheel 30, the film rotates the sprocket 34 and inturn the cam 70 above in the same direction.

[0031] The cam 70 has an upper circular disc portion 71 (shown in dottedlines to allow the features below to be seen) having a side cutout 72and a lower radially expanding cam portion 73 having a radial step 74,the cutout 72 being formed immediately in front of the step 74 below.The cam portion 73 is arranged to be in side contact with the thirdprojection 53 of the striker 50 for, upon rotation by the sprocket 34and through a cam action, turning the striker 50 in the oppositeclockwise direction against the action of a spring 90. The striker 50will stop turning when its third projection 53 reaches and interlocksfrom below with the cutout 72, the striker moving upwards under thecontinual upward action of the same spring 90. At this time, all theaforesaid rotating and turning actions stop and the film advancement isjust completed. At this position a lug 80 on the first projection 51 isurged up to engage the film advance wheel 30 from below preventing itfrom being rotated. The sprocket wheel 34 also cannot be rotated as thecam 70 is prevented from rotating by the third projection 53.

[0032] At such time, the film strip has just been advanced for one frameand the trigger mechanism 140 is primed or re-cocked ready for action topermit photographic exposure on the film strip. For this purpose, theuser is required to depress a trigger button (not shown) which engagesthe top 92 of the striker's axle for moving the striker 50 downwards torelease the third projection 53 is urged to turn back quickly under theaction of the spring to have its second projection 52 stroking theshutter plate end S as described above. The projection 80 is then clearof the film advance wheel 30 which can then be rotated to wind on thefilm.

[0033] It is arranged that the sprocket gear 34 is positioned on the cam70 so that at the position in which the alignment tooth 42 is extendingexactly rearwardly towards the film, the shutter mechanism is re-cockedand the sprocket 34 cannot be moved any further. Thus, the position ofthe alignment tooth 42 is precisely defined and cannot be varied by theperson installing the film, whereby precise alignment of the filmbearing pre-exposed images with the film frame can be readily achieved.

[0034] In use, the user opens the camera back as shown in FIG. 1. Thefilm door 24 will have been previously removed to remove the exposedfilm, or in the case of a new camera, is detached.

[0035] The sprocket gear 34 must be rotated manually in ananti-clockwise sense (viewed from above) or rightward direction (viewedtowards the rear of the camera) until it can be rotated no further atwhich position the alignment tooth 42 will point exactly rearwardlytowards the film.

[0036] As shown in FIGS. 2 and 3 a film package is fitted into the filmchambers with the alignment notch 21 aligned with the alignment tooth42. The film door is fitted and camera back closed. In this position thefilm counter will show the number of exposures remaining eg 27exposures, as shown in FIG. 4. The camera is then ready for use by theuser with the film precisely aligned therein.

[0037] In an alternative modification, instead of forming the alignmenttooth 42 as a separate part, the sprocket wheel can instead have alleight teeth formed unitarily, and the alignment tooth can be painted aseparate colour or coated in some other way to give a contrasting colourto the other seven teeth.

[0038] In a still further alternative the alignment tooth isdistinguished by some other indicating means such as use of a marking,indicia or symbol or letters or similar.

[0039] In a still further alternative the alignment tooth may have adifferent shape to distinguish it from the other seven teeth.

[0040]FIG. 5 also shows a film frame counter 100. The counter 100 has aplurality of peripheral teeth, and markings indicative of the number offilm frames remaining and is supported on the top plate 31. It is drivenfor rotation by a drive wheel 102 formed unitarily with the top of thecam 70. Thus, as the cam 70 rotates as film is wound on the counter 100rotates, by a single tooth for each film frame.

[0041] Unlike a conventional film frame counter wheel which is mountedto rotate about a fixed pivot point, the counter wheel 100 is mounted ona movable axis.

[0042] More particularly, a lever 104 is provided which is itselfmounted on the top plate 31 and beneath the counter 100 (note that theoverlying portion of the counter is cutaway in the drawings to showthis) to pivot about point P. At one end 105 the lever 104 supports thefilm frame counter wheel in a manner to allow rotation. At the other end106 the lever 104 is provided with an actuating surface which bearsagainst the inside of the camera back 8 when the back is closed, asdiscussed further below.

[0043] The film counter wheel 100 is provided with resilient means inthe form of a coil spring 100 which extends between a claw 110 on thetop plate and a short finger 112 depending on the underside of the filmframe counter wheel 100 adjacent to the pivot.

[0044] When the camera back is open the lever 104 is unconstrained bythe back and the force of the spring 108 (FIG. 8) urges the lever 104 inthe direction of the arrow A in FIG. 1 and pulls the axis of the filmframe counter wheel 100 away from the counter wheel drive gear 102 sothe periphery is disengaged therefrom. The film frame counter wheel 100is thereby unconstrained by the drive gear 102 and will rotate to adoptthe position shown in FIG. 8 where the lever abuts a stop 114 on theunderside of the top plate 31.

[0045] After insertion of film into the camera, the camera back isclosed so that the back bears against the actuating end 106 of the lever104 urging this to pivot through a small angle in the direction of thearrow B in FIG. 6. In this position the edge of the film frame counterwheel 100 bears against the counter wheel advancing drive gear 102. Inthis position a “start” or S mark on the film frame counter 100 will bealigned with the frame counter window 116 on the top of the outer camerahousing.

[0046] As can be seen in FIGS. 6 to 8, the actuating end 106 of thelever 104 is joined to the portion which is pivotably mounted on the topplate through a narrowed region which accords a degree of resilience.This gives the bearing of the film frame counter wheel 100 against thedrive gear 102 a degree of resilience so that a continues bearing forceis supplied to the gear wheel and means that excessive force is notimparted to the drive gear 102.

[0047] As pictures are successively taken and the film is advanced, thedrive gear rotates 102 once for each film frame advanced, and for eachrotation of the drive gear 102 the film frame counter wheel 110 isrotated in a clockwise sense by a distance corresponding to one tooth.As the film is advanced and the counter wheel 100 progressively rotatesthe spring 108 becomes increasingly extended, and becomes increasinglywrapped around the pivot. FIG. 7 shows the end of the spring 108 in aposition corresponding to 12 exposures remaining on the film.

[0048] When the end of the film is recorded the film is removed by theuser through the film door. In order to reload the camera, the cameradoor is opened, and when this occurs the pivoting of the lever to theposition described above and shown in FIG. 8 is allowed and the rotationof the counter wheel 100 also allowed, thereby automatically re-settingthe film counter so the start mark S appears in the counter window 116.

[0049] The mechanism described allows for automatic re-setting of theframe counter.

1. A camera for use with film bearing a series of latent pre-exposedimages for subsequent user-exposure, comprising a film sprocket wheelextending into a film passageway, the sprocket wheel comprising a wheelhaving a plurality of equidistantly-spaced teeth one of which isvisually distinguishable from other teeth.
 2. A camera according toclaim 1 wherein the alignment tooth is formed of a different colour tothe other teeth.
 3. A camera according to claim 2 wherein the alignmenttooth is painted in a different colour to the other teeth.
 4. A cameraaccording to claim 1 wherein the sprocket wheel comprises a main wheelpart on which said other teeth are formed, and said alignment tooth isformed of a separate part securable to said main wheel part.
 5. A cameraaccording to claim 4 wherein the main wheel part and the alignment toothare formed of moulded plastics parts where the plastics are ofcontrasting colour.
 6. A camera according to claim 4 wherein the mainwheel defines a part-annular recess, and where the alignment toothextends from a part-annular insert receivable in said recess.
 7. Acamera according to claim 1 where the sprocket wheel is operativelyconnected to a shutter mechanism and wind-on mechanism where rotation ofthe sprocket wheel is arranged to effect re-cocking of the shuttermechanism.
 8. A camera according to claim 4 wherein the wind-onmechanism prevents rotation of the sprocket wheel when the shutter is recocked.
 9. A camera according to claim 5 wherein in the re-cocked stateof the shutter mechanism the alignment tooth extends rearwardly withinthe camera towards the film passageway.
 10. A sprocket wheel for acamera which is, in use, driven by film advanced thereover, comprising asprocket wheel extending into a film passageway having a plurality ofteeth which in use engage in film perforations and which is rotated asthe film is advanced, the sprocket wheel comprising a wheel having aplurality of equidistantly-spaced teeth one of which is visuallydistinguishable from other teeth.
 11. A sprocket wheel according toclaim 10 wherein the alignment tooth is formed of a different colour tothe other teeth.
 12. A sprocket wheel according to claim 10 whichcomprises a main wheel part on which said other teeth are formed, andsaid alignment tooth is formed of a separate part securable to said mainwheel part.
 13. A sprocket wheel according to claim 12 wherein the mainwheel part and the alignment tooth are formed of moulded plastics partswhere the plastics are of contrasting colour.
 14. A method of loadingfilm bearing a series of pre-exposed latent images for subsequentuser-exposure into a camera having a film sprocket wheel operativelyconnected to a shutter mechanism and provided with a film alignmenttooth, comprising the steps of: a) opening the camera back; b) rotatingthe film sprocket wheel until the film alignment tooth thereof extendstowards the film passageway, and until the shutter mechanism isre-cocked; c) inserting film into the camera so that an alignment markon the film is aligned with the alignment tooth; and d) closing thecamera back.
 15. A camera having a pair of film-receiving chambersarranged on opposites sides of an exposure window between which, in use,film extends through a film passageway: a film sprocket wheel having aplurality of teeth which, in use, engage a film extending within thefilm passageway; a film counter drive wheel operatively connected to thefilm sprocket wheel driven by rotation of the sprocket wheel; a filmframe counter wheel mounted on a movable pivot engageable with the drivewheel; and resilient means which urge the film frame counter wheel to areset position in which the film frame counter wheel adopts a predefinedorientation.
 16. A camera according to claim 15 wherein the pivot forthe film frame counter wheel is mounted to allow displacement between aposition in which the counter wheel and drive gear are engaged, and aposition in which they are separated.
 17. A camera according to claim 15wherein the said resilient means acts on the pivot to urge the counterwheel to the disengaged position.
 18. A camera according to claim 17wherein the pivot for the counter wheel is mounted on a lever which ismovable to allow movement of the counter wheel into and out ofengagement with the drive gear.
 19. A camera according to claim 18wherein an end of the lever opposite to the mounting of the counterwheel bears against a door of the camera, whereby when in a closedposition the door bears against the lever and urges the counter wheeland drive gear into engagement.